Cellulose-acrylonitrile polymer solutions, articles, and methods of making same

ABSTRACT

New polymer solutions, processes for producing such solutions, shaped articles made from these solutions, and process of making such articles, are disclosed. The polymer solutions contain cellulose having a degree of polymerization of at least 200, an acrylonitrile polymer, dimethylsulphoxide and formaldehyde. The weight ratio of cellulose/acrylonitrile polymer is 0.05 to 1, preferably 0.1 to 1, the weight ratio of formaldehyde/cellulose is 0.2 to 2, and the total concentration of polymer in the solution is 12 to 30% by weight, preferably 18 to 26% by weight. 
     The solutions of the present invention are particularly suitable for the production of filaments consisting of fibrils orientated approximately along the axis of the fibre and closely interwoven, with the cellulose macromolecules being partially involved in a crystal lattice characteristic of cellulose II. The filaments possess valuable properties for use in textiles, such as, for instance, in garments.

This is a division application of Ser. No. 147,221, filed May 6, 1980,now U.S. Pat. No. 4,377,648.

The present invention relates to shapable solutions of cellulose andacrylonitrile polymers, which can be shaped and converted to yarns,fibres, films, membranes, coatings and the like, to a process for thepreparation of such solutions, to yarns and fibres obtained from thesesolutions, and to the process for producing such yarns and fibres.

BACKGROUND OF THE INVENTION

East German Pat. No. 94,493 discloses solutions which can be convertedinto yarns and films. The solutions are prepared by dissolving celluloseand another polymer, such as polyacrylonitrile, in aqueous zinc chloridesolutions, having a zinc chloride concentration of 30-70% and optionallycontaining a minor amount of an acid, such as formic acid, phosphoricacid, hydrochloric acid or the like. A disadvantage of this technique isthat solutions based upon zinc chloride cause hydrolysis and thereforedegradation of the cellulose polymer.

Published Japanese Patent Application No. 71/27,573, published on Aug.10, 1971, discloses the preparation of solutions or dispersions ofmixtures of cellulose and polymers such as acrylonitrile polymers insulphur dioxide, in the presence of a tertiary or secondary amine.Because of the particular compounds used in the disclosed process, it isnecessary when using such solutions to take particular precautions asregard hygiene and safety; and the solutions of this published JapanesePatent Application cannot easily be used in industrial processes.

An article by Raymond B. Seymour and Earl J. Johnson in "Struct.Solubility Relat. Polym. (Proc. Symp.), 1976, pages 241-244 (published1977)" describes the possibility of obtaining fibres ofpolyacrylonitrile and cellulose from solutions. However, the startingcellulose solutions have a concentration of less than 2.5%, and it isnot possible to obtain fibres having valuable textile properties fromsuch solutions, so that the article does not lead to a process suitablefor industrial production.

East German Pat. No. 89,003 teaches the preparation of stabledispersions by introducing microcrystalline cellulose into a solution ofanother polymer. The cellulose introduced in this manner is still in aparticulate state at the fibre state, and does not contribute textileproperties to the fibres.

SUMMARY OF THE INVENTION

The present invention in one aspect includes shapable or spinnablesolutions which comprise cellulose, acrylonitrile polymer, formaldehyde,and dimethylsulphoxide wherein the weight ratio of cellulose/acrylicpolymer is 0.05 to 1, preferably 0.1 to 1, the weight ratio offormaldehyde/cellulose is 0.2 to 2, and the total polymer concentrationin the solution is from 12 to 30% by weight, preferably 18 to 26%. Thecellulose has a degree of polymerisation of at least 200. Fibres andfilaments prepared from the solutions of the present invention have bothof the polymers in the form of fibrils closely intermingled andsubstantially orientated along the fibre axis. The macromolecules ofcellulose are partially bound in a crystalline network which ischaracteristic of cellulose II. When the preferred weight ratio ofcellulose/acrylic polymer is between 0.1 and 1, both polymericconstituents form a tri-dimensional endless network, whereas for a ratioof cellulose/acrylic polymer of between 0.05 and 0.1, the acryliccomponent alone forms an endless network, with the cellulose polymerbeing in the form of discontinuous fibrils. To obtain yarns and fibres,it is preferred to utilize solutions having a polymer concentration ofbetween 18 and 26% by weight, a water content which is less than orequal to 5,000 ppm, and a weight ratio of cellulose/acrylic polymer ofbetween 0.1 and 1.

The present invention also relates to a process for preparing theshapable solutions of the present invention, by adding the acrylonitrilepolymer in powder form to a solution, in a mixture of dimethylsulphoxideand formaldehyde, of cellulose having a degree of polymerisation of atleast 200 and previously dried. The total polymer concentration isbetween 12 and 30%, and the weight ratio of cellulose/acrylic polymer isbetween 0.05 and 1. The cellulose solution may be in the form of apowder previously crystallised by cooling a solution to a temperaturebelow 17° C., preferably of between 0° and 5° C., and in this case thetwo polymers are mixed, for example in a malaxating extruder, at atemperature between 90° and 150° C., preferably between 100° and 135° C.

It is also possible to obtain the solutions of the present invention byseparately dissolving the acrylic polymer in dimethylsulphoxide and thecellulose in a mixture of dimethylsulphoxide and formaldehyde, and thenmixing the two solutions while stirring, with the weight ratio ofcellulose/acrylic polymer being between 0.05 and 1. This latter processis generally preferred for the preparatiion of solutions having a totalpolymer concentration of between 12 and 18% by weight.

The present invention also relates to filaments, fibres and yarnsproduced from the solutions of the present invention. These fibres,filaments and yarns are based on cellulose and acrylic polymers in aweight ratio of cellulose/acrylic polymer of between 0.05 and 1. Inthese filaments, fibres and yarns each polymer is in the form of fibrilsorientated approximately along the axis of the fibre and closelyinterwoven with one another. The fibrils of the acrylic constituent forma continuous three-dimensional system over the whole length of thefibre, whereas the cellulose macromolecules are partially involved in athree-dimensional crystal lattice characteristic of cellulose II.Preferably the weight ratio of cellulose/acrylic polymer is between 0.1and 1, and the cellulose fibrils also form a continuousthree-dimensional fibrillar system. The higher the proportion ofcellulose, the denser the system, with the fibrils of the twoconstituents being intimately intermixed.

The yarns and fibres produced according to the present invention possessa water retention capacity of at least 20, preferably at least 30, asdetermined in accordance with DIN Standard Specification 53-814.

The present invention also relates to a process for producing the yarnsand fibres of the present invention, by wet spinning the solutions ofthe present invention. The total polymer concentration in thesesolutions is between 12 and 30%, and the solutions are spun into acoagulating bath consisting of 25 to 80% by volume of water and 75 to20% by volume of dimethylsulphoxide. The coagulating bath is maintainedat between 0° and 40° C., and the filaments may thereafter be subjectedto orientation and solvent removal using standard processing conditions.

DETAILED DESCRIPTION OF THE INVENTION

The cellulosic polymer used in the solutions of the present inventionmay be cellulose I, referred to as native cellulose, of any suitableorigin, for example, cotton linters or wood pulp, or the cellulose maybe cellulose II possessing a degree of polymerisation of at least 200and originating, for example, from waste fibres or films of regeneratedcellulose or alkali cellulose, which has been neutralised and washed.

The acrylonitrile polymers or acrylic polymers of the present inventionare polymers containing at least 50% by weight of acrylonitrile units,and preferably at least 85% of acrylonitrile units. The remainder of thepolymer, that is, up to 50% by weight, and preferably only up to 15% byweight, may be units derived from one or more copolymerisableethylenically unsaturated monomers, and especially those ethylenicallyunsaturated monomers which are normally copolymerised withacrylonitrile, such as vinyl compounds, including, for instance, vinylchloride and vinyl acetate, acrylic or methacrylic acid, acrylic ormethacrylic acid esters and acrylamide or methacrylamide, andmethacrylonitrile. Other ethylenically unsaturated monomers which can beutilized include compounds having a carboxylic acid group, such asitaconic acid, or compounds having a sulphonic acid group, such asvinyl-sulphonic acid compounds, allyl- and methallyl-sulphonic acids,sulphonated aromatic derivatives, styrene-sulphonic acid,vinyloxyarenesulphonic acids, vinyl deriatives of the basic type, suchas vinylpyridine and its alkylated derivatives, and vinyl dialkylamineenters, and the like. Mixtures of varying proportions of acrylonitrilecopolymers listed above may be utilized, including mixtures withacrylonitrile homopolymers. The polymers are, of course, in the filmforming molecular weight range.

The starting cellulose, having a degree of polymerisation of at least200, is cut up, dried if necessary, and then pre-swollen in DMSO(dimethylsulphoxide) which has been previously dried if required.Thereafter the formaldehyde, preferably in the form of paraformaldehyde,is added to the mixture, and the temperature is raised to a value whichis preferably within the range of 90° to 140° C., in accordance with theprocess described in commonly assigned published French Application No.2,358,435, published on Feb. 10, 1978, the disclosure of which is herebyincorporated by reference.

The weight ratio of formaldehyde/cellulose largely depends upon theparticular cellulose which is used. That is, the lower the accessibilityof the cellulose employed, the higher the ratio offormaldehyde/cellulose which is preferably used. In practice, in orderto dissolve cellulose I, a weight ratio of formaldehyde/cellulose of atleast 1 is preferably utilized, whereas for cellulose II, it is possibleto use a ratio of at least 0.6 at the dissolution stage. In order tofacilitate subsequent conversion, the ratio of formaldehyde/cellulosecan be reduced, if desired, after dissolution, to a value of between 0.2and 2 by removing the formaldehyde by any known means, such asentrainment by means of an anhydrous and preferably inert gas, ordistillation under reduced pressure, without risk of gel formation orcoagulation, provided, however, that the ratio of formaldehyde/celluloseis always at least equal to 0.2.

Preferably the formaldehyde used in the present invention is in the formparaformaldehyde.

It is desired that the water content of the various reactants be low,for instance, that the water content of the cellulose is less than 1%,that of the dimethylsulphoxide be less than or equal to 1%, and that ofthe paraformaldehyde be less than 4% by weight.

The solution of the acrylic polymer is dimethylsulphoxide can beprepared in the cold, under ambient conditions, or under the action ofheat, depending upon the particular case, simply while stirring, and thetwo polymeric solutions can then be mixed while stirring, at theindicated weight ratio of cellulose/acrylic polymer of between 0.05and 1. This mixing of two polymeric solutions is preferably used whenthe polymer concentration is relatively low, that is, generally fromabout 12 to 18% by weight.

In order to obtain polymeric solutions having a higher polymerconcentration (up to 30% by weight) or, in the case of cellulosesolutions of high viscosity (high degree of polymerisation and/or highconcentration), it is generally preferred to add the acrylic polymerdirectly in powder form, either to the cellulose solution prepared asdescribed above, or to a powder produced by crystallising a cellulosesolution prepared as described above, by cooling the cellulose solutionto a temperature below 17° C., preferably between 0° and 5° C.

The two powders are then mixed, for example in a malaxating extruder, ata temperature between 90° and 150° C.

The solutions of the present invention can be modified before they areshaped or spun, in order to improve the properties of the resultingarticles. For instance, a minor proportion of an additive such as dyes,pigments, flame-proofing agents such as, for instance, polymerisedphosphorus and/or sulphur containing compounds, and the like, may beadded using conventional techniques to the solutions of the presentinvention.

The solutions of the present invention can be used to produce quitediverse articles, such as yarns, fibres, films, sheets, coatings and thelike.

The solutions of the present invention which are suitable for spinningare those solutions which have a total polymer concentration of between12 and 30% by weight, a ratio of cellulose/acrylic polymer of between0.05 and 1 and a water content of less than 5,000 ppm. However, in orderto conduct the spinning operation profitably on an industrial scale, andto obtain fibres having good characteristics, the polymer concentrationshould be at least 18% by weight, preferably between 18 and 26% byweight, and the ratio of cellulose/acrylic polymer should be between 0.1and 1. These solutions can be spun dry in accordance with any processknown to those skilled in the art, for example, in accordance with theprocess of published French Patent Application No. 2,372,251, publishedon June 23, 1978, the disclosure of which is hereby incorporated byreference. Preferably, however, the solutions of the present inventionare spun into a coagulating bath which consists essentially of water anddimethylsulphoxide in respective proportions of between 25/75 and 80/20by volume, with the bath maintained at a temperature between 0° and 40°C. The filaments are subjected to a molecular orientation, which can becarried out in the coagulating bath, or subsequent to the coagulatingbath, by drawing in one or more stages, for example in air, in anaqueous bath, or in both the latter in succession.

After the filaments have left the coagulating bath, they are freed ofsolvent by washing with water before, during or after drawing. Thewashing can also be conducted using dilute ammonia solutions, in orderto prevent the strands from sticking. In this instance, the filamentscan advantageously be washed with water and then sized and dried.

For a ratio of cellulose/acrylonitrile polymer of between about 0.05 and0.1, the yarns and fibres produced according to present inventioncomprise a continuous three-dimensional system consisting of anacrylonitrile polymer of which the fibrils, which are orientatedapproximately in the direction of the axis of the fibre, and are in theform of a continuous three-dimensional system, are closely intermixedwith cellulose fibrils which are orientated approximately along the axisof the fibre but remain discontinuous. For a ratio of cellulose/acrylicpolymer of between 0.1 and 1, however, the cellulose fibrils becomedenser and also form a continuous three-dimensional system. Thecellulose macromolecules in all cases are partially involved in athree-dimensional crystal lattice characteristic of cellulose II.

The yarns and fibres of the present invention, obtained from thesolutions of the present invention, simultaneously possess goodmechanical properties, a good absorption capacity, good dyeing affinity,and excellent antistatic properties. The water retention capacity of theyarns and fibres of the present invention may be determined inaccordance with DIN Standard Specification 53-814. The water retentioncapacity is at least 20, preferably at least 30, and normally will liebetween 20 and 80, more preferably between 30 and 80. In contrast, thewater retention capacity of acrylic fibres containing no cellulose willbe in the order of 5-6. This characteristic makes the fibres verycomfortable to wear, since they rapidly absorb body moisture, which canthen evaporate from the surface of textile.

Using solutions of the present invention, it is also possible to obtainfilms, sheets, coatings and the like, in accordance with any knownprocess.

DESCRIPTION OF THE DRAWINGS

The invention will be more clearly understood with reference to theaccompanying figures, wherein

FIGS. 1 to 4 show (magnification of 200×) the fibrillar cellulose systemby itself, obtained after dissolving the acrylic constituent from thefibres, of fibres obtained from solutions containing increasingproportions of cellulose/acrylic polymer, as follows:

FIG. 1: ratio cellulose/acrylic polymer 0.05

FIG. 2: ratio cellulose/acrylic polymer 0.1

FIG. 3: ratio cellulose/acrylic polymer 0.2

FIG. 4: ratio cellulose/acrylic polymer 0.4

FIG. 5 illustrates (magnification of 6,000×) a sectional view of thecomplete yarn or FIG. 4, prior to the acrylic constituent dissolvingstep. The yarn contains two fibrillar systems, which can be clearlyseen.

EXAMPLES OF THE INVENTION

The invention will be understood more readily from the followingexamples, wherein parts and percentages are by weight unless indicatedotherwise.

EXAMPLE 1

106 g of bleached "Kraft" paper wood pulp, having a cellulose degree ofpolymerization of 1050 and a moisture content of 6%, were completelydried in an oven and then introduced into 1467 g of dimethylsulphoxidecontaining 230 ppm of water. Thereafter 124.8 g of 96% pureparaformaldehyde was added to the mixture, with a resultingformaldehyde/cellulose weight ratio of 1.2.

The mixture was heated for 6 hours 135° C. while stirring, andthereafter a portion of the formaldehyde was removed by continuouspassage through a thin film evaporator in vacuuo until a weight ratio offormaldehyde/cellulose of 0.40 was obtained, resulting in a solutionhaving a viscosity of 2200 poises at 20° C.

The solution was then cooled to 85° C. and thereafter a solution of anacrylonitrile polymer, which was a copolymer containing 91.4% by weightof acrylonitrile, 7.75% by weight of methyl methacrylate and 0.85% byweight of sodium methyallylsulphonate in dimethylsulphoxide (at aconcentration of 23% by weight of polymer) was added so as to obtain aweight ratio of cellulose/acrylic polymer of 0.05. The mixture of thetwo solutions was malaxated for 1 hour at 85° C., and then the resultinghomogeneous solution, containing 20.4% by weight of polymer, wasextruded through a spinneret having 200 orifices, each orifice ofdiameter of 0.055 mm, into a coagulating bath maintained at 5° C. Thecoagulating bath consisted of dimethylsulphoxide and water in respectiveportions of 55/45 by volume.

Upon leaving the coagulating bath, the yarns were taken up and thendrawn in air at the ambient temperature, between two pairs of rollers,in a ratio of 1.3×, washed with water on the second pair of rollers, anddrawn again in a bath of boiling water in a ratio of 4.1×. The finalyarn speed was 55 m/minute. The sized and dried filaments had thefollowing characteristics:

    ______________________________________                                        Gauge per strand       1.7 dtex                                               Tensile strength       28 g/tex                                               Elongation             21%                                                    Water retention capacity                                                                             22.                                                    ______________________________________                                    

EXAMPLE 2

106 g of prehydrolysed sulphate pulp, having a cellulose degree ofpolymerization of 430 and a moisture content of 6%, were completelydried in an oven and homogeneously mixed with 436 g ofdimethylsulphoxide, containing 300 ppm of water, and 135 g ofparaformaldehyde (corresponding to a ratio paraformaldehyde/cellulose of1.3). The resulting mixture was heated for 8 hours at 110° C. and thenfor 7 hours at 135° C., while stirring.

A portion of the formaldehyde was then removed, as in Example 1, so asto obtain a ratio of formaldehyde/cellulose of 0.47. The solution thusobtained, which had a viscosity of 4400 poises at 90° C., was cooled toa temperature of 3° C., powdered and mixed cold with a dry acrylonitrilepolymer having a composition identical to that described in Example 1,so as to produce a ratio of cellulose/acrylic polymer of 1. The polymerconcentration in the solution was 29.3% by weight. The mixture waspassed through a twin-screw degassing extruder at a temperature of 130°C. and was then extruded through a spinneret having 200 holes, each of adiameter of 0.055 mm, at 90° C., into a coagulating bath maintained at5° C., and containing dimethylsulphoxide and water in a 55/45 proportionby volume.

The filaments were successively subjected to drawing in air at ambienttemperature in a ratio of 1.3×, washed with water at ambient temperatureand drawn in boiling water in a ratio of 4×. The final yarn speed was 40m/minute. The resulting filaments, after sizing and drying, had thefollowing characteristics:

    ______________________________________                                        Gauge per strand       3.3 dtex                                               Tensile strength       21 g/tex                                               Elongation             15%                                                    Water retention capacity                                                                             72.                                                    ______________________________________                                    

EXAMPLE 3

106 g of bisulphite pulp, having a cellulose degree of polymerization of770 and a moisture content of 6%, were completely dried in an oven andthen introduced into 885 g of dimethylsulphoxide containing 520 ppm ofwater. 125 g of 96% pure paraformaldehyde were added so as to obtain aratio of paraformaldehyde/cellulose of 1.20. The resulting mixture washeated for 6 hours at 135° C. while stirring. After that time, thecellulose was dissolved in solution, and thereafter the ratio ofparaformaldehyde/cellulose was reduced to 0.35 in the same manner as inExample 1. The resulting solution had a viscosity of 400 poises at 85°C.

After cooling to ambient temperature, 250 g of an acrylonitrile polymerwhich was identical to that described in Example 1 was added to thecellulose solution, so as to obtain a weight ratio of cellulose/acrylicpolymer of 0.4. The mixture was malaxated for 1 hour at ambienttemperature, and then 200 g of dimethylsulphoxide were added to themixture, and the resulting mixture was malaxated again for 1 hour at 85°C.

The resulting homogeneous solution, which had a total polymerconcentration of 23.8% by weight, was extruded through a spinnerethaving 200 orifices, each of diameter of 0.055 mm, into a coagulatingbath containing dimethylsulphoxide and water (55/45 proportion byvolume) and maintained at 5° C. The filaments having the coagulatingbath were drawn in air in a ratio of 1.07×, washed with water at ambienttemperature and drawn in boiling water in a ratio of 4.1×. The finalyarn speed was 60 m/minute.

The resulting filaments, after sizing and drying, had the followingproperties:

    ______________________________________                                        Gauge per strand       3.3 tex                                                Tensile strength       25 g/tex                                               Elongation             14%                                                    Water retention capacity                                                                             48.                                                    ______________________________________                                    

EXAMPLE 4

106 g of prehydrolysed sulphate "Kraft" paper pulp, having a cellulosedegree of polymerization of 500 and a moisture content of 6%, werecompletely dried in an oven and then introduced into 1440 g ofdimethylsulphoxide containing 550 ppm of water. 125 g of 96% pureparaformaldehyde were added so as to obtain a ratio ofparaformaldehyde/cellulose of 1.20.

The resulting mixture was heated for 5 hours at 135° C. while stirring.After the cellulose dissolved, some of the formaldehyde was removed bybubbling a stream of dry nitrogen through the solution at 120° C., andby this means the ratio of formaldehyde/cellulose was lowered to 0.25.

The resulting solution, which has viscosity of 410 Poises at 20° C., wascooled to ambient temperature and then 500 g of an acrylonitrile polymerwhich was identical to the acrylic polymer used in Example 1 was addedin powder form to the solution so as to obtain a ratio ofcellulose/acrylonitrile of 0.2. The mixture was malaxated for 1 hourunder ambient conditions, and then 250 g of dimethylsulphoxide wereadded to the mixture, and then the mixture was malaxated again for 1hour at 85° C. The resulting solution, containing 25.9% by weight ofpolymer, was extruded at 75° C. through a spinneret having 200 orifices,each of diameter of 0.055 mm, into a coagulating bath maintained at 5°C. and consisting of a mixture of dimethylsulphoxide and water in aproportion of 55/45 by volume.

The filaments were extracted from the coagulating bath by positivelydriven mechanical device and drawn in air in a ratio of 1.4×, washed bycounter-current flow water under ambient conditions and drawn in boilingwater at a ratio of 4.1×. The final filament speed was 60 m/minute. Theproperties of the resulting yarns, after being sized and dried, is setforth in Table 1 below.

EXAMPLES 5-9

Example 4 was repeated, with identical solutions extruded through thesame spinneret, but into coagulating baths having different compositionsand at different temperatures, and under different drawing conditions,with the differences in conditions, and the characteristics of theresulting filaments, are set forth in Table 1 below.

                  TABLE 1                                                         ______________________________________                                               Examples                                                                      4     5       6       7     8     9                                    ______________________________________                                        Coagulating                                                                   bath                                                                          Proportion                                                                             55/45   55/45   70/30 70/30 35/65 35/65                              of DMSO/                                                                      water                                                                         Temperature                                                                            5       35      5     15    5     35                                 °C.                                                                    Drawing ratio                                                                 Drawing in                                                                             1.4     1.4     1.17  1.17  1     1                                  air                                                                           Drawing in                                                                             4.1     4.1     4.9   4.9   5.5   5.5                                boiling                                                                       water                                                                         Final speed                                                                            60      60      50    50    55    55                                 m/minute                                                                      Tensile  30      26      31    28    29    27                                 strength g/tex                                                                Elongation %                                                                           16      15      16    15    16    16                                 Water    40      38      41    43    44    40                                 retention                                                                     capacity                                                                      ______________________________________                                    

EXAMPLE 10

106 g of prehydrolyzed sulphate "Kraft" pulp, having a cellulose degreeof polymerisation of 500 and a moisture content of 6%, were completelydried in an oven and then introduced into 1,440 g of dimethylsulphoxidecontaining 550 ppm of water. 125 g of 96% pure paraformaldehyde wereadded to the mixture so as to obtain a ratio ofparaformaldehyde/cellulose of 1.20. The mixture was heated for 5 hoursat 135° C. and then cooled to ambient temperature. Then 500 g of a drypowdered acrylonitrile polymer, containing 94.15% by weight ofacrylonitrile units, 5% by weight of methyl methacrylate units and 0.85%by weight of sodium methallylsulphonate units, were added so as toobtain a ratio of cellulose/acrylic polymer of 0.2. The mixture wasmalaxated for 1 hour under ambient conditions, 250 g ofdimethylsulphoxide were then added, and then the mixture was malaxatedagain for 1 hour at 85° C. The resulting solution, containing 24.8 % byweight of polymer, was extruded at 75° C. through a spinneret having 200orifices each of a diameter of 0.055 mm into a coagulating bathmaintained at 5° C. and containing a mixture of dimethylsulphoxide andwater in a proportion of 55/45 by volume.

The filaments were extracted from the coagulating bath by a positivelydriven mechanical device and then drawn in air at ambient temperature ina ratio of 1.05×and washed, during the air drying, by spraying with anaqueous ammonia solution having a concentration of 30 g/liter. Thefilaments were subsequently passed through an intermediate tankcontaining an aqueous ammonia solution having a concentration of 30g/liter, and then drawn again in boiling water in a ratio of 4.1×,washed, sized and dried. The resulting filaments possessed thecharacteristics indicated in Table 2 below.

EXAMPLES 11 AND 12

Polymer solutions identical to the solution described in Example 10 wereextruded under the same conditions as in Example 10 into coagulatingbaths, having compositions and temperatures indicated in Table 2 below.The filaments were treated under the drawing conditions identical toExample 10, with the exception of those conditions set forth in Table 2,with the properties of the resulting filaments set forth in Table 2below.

                  TABLE 2                                                         ______________________________________                                                     Examples                                                                      10       11      12                                              ______________________________________                                        Coagulating bath                                                              Proportion of DMSO/                                                                          55/45      70/30   70/30                                       water                                                                         Temperature °C.                                                                       5          25      35                                          Drawing ratio                                                                 Drawing in air 1.05       1.07    1.04                                        Drawing in boiling                                                                           4.1        4.9     5.2                                         water                                                                         Final speed in 50         50      50                                          m/minute                                                                      Properties                                                                    Tensile strength g/tex                                                                       25         25      26                                          Elongation %   14         13.5    15                                          Water retention                                                                              42         39      40                                          capacity                                                                      ______________________________________                                    

EXAMPLE 13

Example 4 was repeated, using an identical cellulose solution, and withan acrylonitrile homopolymer in place of the acrylic polymer of Example4, but with the polymers in the same proportions, and with 935 g ofdimethylsulphoxide, instead of the 250 g of Example 4, added aftermalaxation under ambient conditions. The filaments were extruded anddrawn in the same manner as in Example 4, except that the temperature ofthe coagulating bath was 15° C. The filaments possess the followingproperties:

    ______________________________________                                        Tensile strength       28 g/tex                                               Elongation             14%                                                    Water retention capacity                                                                             41.                                                    ______________________________________                                    

EXAMPLE 14

Example 4 was repeated, using the same cellulose solution, with theacrylonitrile polymer of Example 4 replaced by an identical proportionof a copolymer having the following composition:

    ______________________________________                                        acrylonitrile       92.70  parts by weight                                    vinyl acetate       6.60   parts by weight                                    sodium methallylsulphonate                                                                        0.70   parts by weight                                    ______________________________________                                    

The resulting solution was extruded under the conditions of Example 4into a coagulating bath containing a mixture of dimethylsulphoxide andwater in proportions of 35/65 by volume, and maintained at 25° C. Theresulting filaments were treated as in Example 4, but the draw ratio inair was reduced to 1× (which meant that no drawing took place during thepassage in air). The air draw step was followed by washing with water atambient temperature, and drawing in boiling water in a ratio of 5.5×,sizing and drying. The resulting filament had the followingcharacteristics:

    ______________________________________                                        Tensile strength       28 g/tex                                               Elongation             15%                                                    Water retention capacity                                                                             39.                                                    ______________________________________                                    

EXAMPLE 15

106 g of prehydrolysed sulphate "kraft" pulp, having a cellulose degreeof polymerisation of 500 and a moisture content of 6%, were completelydried in an oven and then introduced into 1,440 g of dimethylsulphoxidecontaining 550 ppm of water. 125 g of 96% pure paraformaldehyde wereadded so as to obtain a ratio of paraformaldehyde/cellulose of 1.20.

The resulting mixture was heated for 5 hours at 135° C. while stirringto dissolve the cellulose. After dissolution, some of theparaformaldehyde was removed by bubbling a stream of dry nitrogen at120° C. through the solution, so that the ratio offormaldehyde/cellulose was lowered to 0.25.

The resulting solution, which had a viscosity of 410 Poises at 20° C.,was cooled, and 1,000 g of a dry acrylonitrile polymer, which wasidentical to the acrylic polymer of Example 1, was added in powder form,so as to obtain a ratio of cellulose/acrylonitrile polymer of 0.1. Themixture was malaxated for 1 hour under ambient conditions, 3,545 g ofdimethylsulphoxide were added, and then the mixture was malaxated for 1hour at 85° C. The resulting solution, containing 18% by weight ofpolymer, was extruded at 75° C. through a spinneret having 200 orificesof 0.055 mm diameter into a coagulating bath maintained at 5° C. andconsisting of a mixture of dimethylsulphoxide and water in a volumeproportion of 55/45. The filaments were extracted from the coagulatingbath by a positively driven mechanical device and then drawn in air in aratio of 1.1×, washed countercurrently and drawn in boiling water in aratio of 4× , sized and dried. The filament speed was 50 m/minute. Theresulting filaments had the following properties:

    ______________________________________                                        Gauge per strand       3.3 dtex                                               Tensile strength       23 g/tex                                               Elongation             17%                                                    Water retention capacity                                                                             33.                                                    ______________________________________                                    

EXAMPLE 16

106 g of prehydrolyzed sulphate pulp, having a cellulose degree ofpolymerisation of 500 and a moisture content of 6%, were completelydried in an oven and then homogeneously mixed with 1,500 g ofdimethylsulphoxide containing 500 ppm of water. 125 g of 96% pureparaformaldehyde were added to the mixture in order to obtain a ratio ofparaformaldehyde/cellulose of 1.2. The mixture was heated for 6 hours at135° C. to dissolve the cellulose. After dissolution, the ratio ofparaformaldehyde/cellulose was reduced to 0.30 by passage through a thinfilm evaporator in vacuo at 130° C.

Thereafter 2,000 g of an acrylonitrile polymer, consisting of 91.4% byweight of acrylonitrile units, 7.75% by weight of methyl methacrylateunits and 0.85% by weight of sodium methallylsulphonate units, wereadded to the cellulose solution so as to obtain a ratio ofcellulose/acrylic polymer of 0.05. The mixture was malaxated for 1 hourunder ambient conditions, 7,970 g of dimethylsulphoxide were then addedto the mixture, and the resulting mixture was malaxated again for 1 hourat 85° C.

The resulting solution, which had a total polymer concentration of 18%by weight, was extruded at 75° C. through a spinneret having 200orifices, each of diameter of 0.055 mm, into a coagulating bathcontaining dimethylsulphoxide and water in a volume proportion of 55/45and maintained at 5° C. The filaments leaving the coagulating bath weredrawn in air in a ratio of 1.2, washed with water and then drawn inboiling water in a ratio of 4.1. The final filament speed was 60m/minute. After washing with water, sizing and drying, the resultingfilaments had the following properties:

    ______________________________________                                        Gauge per strand       3.3 dtex                                               Tensile strength       24 g/tex                                               Elongation             16%                                                    Water retention capacity                                                                             23.                                                    ______________________________________                                    

The acrylic polymer phase of the resulting filaments was dissolved, andthe cellulose phase appeared in the form of discontinuous fibrils asshown in FIG. 1.

EXAMPLE 17

106 g of prehydrolysed sulphate pulp, having a cellulose degree ofpolymerisation of 500 and a moisture content of 6%, were completed driedin an oven then homogeneously mixed with 1,500 g of dimethylsulphoxidecontaining 500 ppm of water. 125 g of 96% pure paraformaldehyde wereadded in order to obtain a ratio of paraformaldehyde/cellulose of 1.2.The resulting mixture was heated for 6 hours at 135° C. to dissolve thecellulose. After dissolution, the ratio of formaldehyde/cellulose wasreduced to 0.30 by passage through a thin film evaporator, in vacuo, at130° C. Thereafter, 1,000 g of an acrylonitrile polymer, containing91.4% by weight of acrylonitrile, 7.75% by weight of methylmethacrylate, and 0.85% by weight of sodium methallyl-sulphonate, wereadded to the cellulose solution so as to obtain a ratio ofcellulose/acrylic polymer of 0.1. The mixture as malaxated for 1 hourunder ambient conditions, and 2,870 g of dimethylsulphoxide were thenadded. Thereafter the resulting mixture was malaxated again for 1 hourat 85° C.

The resulting solution, which had a total polymer concentration of 20%by weight, was extruded at 75° C. through a spinneret having 200orifices, each having a diameter of 0.055 mm, into a coagulating bathcontaining dimethylsulphoxide and water in a volume proportion of 55/45and maintained at 5° C. The filaments leaving the coagulating bath weredrawn in air in a ratio of 1.3, washed with water and then drawn inboiling water in a ratio of 4.3. The final speed of the filaments was 60m/minute. After washing with water, sizing and drying, the resultingfilaments had the following properties:

    ______________________________________                                        Gauge per strand       3.3 dtex                                               Tensile strength       31 g/tex                                               Elongation             16%                                                    Water retention capacity                                                                             30.                                                    ______________________________________                                    

After dissolving the acrylic polymer phase from the resulting filaments,the cellulose phase appeared in the form of a system illustrated in FIG.2.

EXAMPLE 18

106 g of prehydrolysed sulphate pulp, having a cellulose degree ofpolymerisation of 500 and a moisture content of 6% were completely driedin an oven and then homogeneously mixed with 1,200 g ofdimethylsulphoxide containing 550 ppm of water. 125 g of 96% pureparaformaldehyde were added in order to obtain a ratio ofparaformaldehyde/cellulose of 1.2. The mixture was heated for 6 hours at135° C. to dissolve the cellulose. After this dissolution the ratio offormaldehyde/cellulose was reduced to 0.30 by passage through a thinfilm evaporator, in vacuo, at 130° C.

Thereafter, 500 g of acrylonitrile polymer, consisting of 91.4% byweight of acrylonitrile units, 7.75% by weight of methyl methacrylateunits and 0.85% by weight of sodium methallylsulphonate units, wereadded to the cellulose solution so as to obtain a ratio ofcellulose/acrylic polymer of 0.2. The mixture was malaxated for 1 hourunder ambient conditions, and then 1,175 g of dimethylsulphoxide wereadded, and thereafter the mixture was malaxated again for 1 hour at 85°C.

The resulting solution, having a total polymer concentration of 20% byweight, was extruded at 75° C. through a spinneret having a 200orifices, each of a diameter of 0.055 mm, into a coagulating bathcontaining dimethylsulphoxide and water in a volume proportion of 55/45and maintained at 5° C. The filaments leaving the coagulating bath weredrawn in air in a ratio of 1.4, washed with water and then drawn inboiling water in a ratio of 4.2. The final filament speed was 60m/minute. After washing with water, sizing and drying, the resultingfilaments had the following properties:

    ______________________________________                                        Gauge per strand       3.3 dtex                                               Tensile strength       30 g/tex                                               Elongation             15%                                                    Water retention capacity                                                                             40.                                                    ______________________________________                                    

The acrylic polymer phase was dissolved from the resulting filaments,with the cellulose phase remaining appearing in the form of a systemillustrated in FIG. 3.

EXAMPLE 19

106 g of prehydrolysed sulphate pulp, having a cellulose degree ofpolymerisation of 500 and a moisture content of 6% by weight wascompleted dried in an oven and then homogeneously mixed with 200 g ofdimethylsulphoxide containing 500 ppm of water. 125 g of 96% pureparaformaldehyde were added in order to obtain a ratio ofparaformaldehyde/cellulose of 1.2. The mixture was heated for 6 hours at135° C. to dissolve the cellulose. After this dissolution, the ratio ofparaformaldehyde/cellulose was reduced to 0.30 by passage through a thinfilm evaporator, in vacuo, at 130° C.

Thereafter, 250 g of an acrylonitrile polymer, consisting of 91.4% byweight of acrylonitrile units, 7.75% by weight of methyl methacrylateunits and 0.85% by weight of sodium methallylsulphonate units, was addedto the cellulose solution so as to obtain a ratio of cellulose/acrylicpolymer of 0.4. The mixture was malaxated for 1 hour under ambientconditions, 200 g of dimethylsulphoxide were then added to the mixture,and the resulting mixture was malaxated again for one hour at 85° C.

The resulting solution, having a total polymer concentration of 24% byweight, was extruded at 80° C. through a spinneret having 200 orifices,each of a diameter of 0.055 mm, into a coagulating bath maintained at 5°C. and containing dimethylsulphoxide and water in a volume proportion of55/45. The filaments leaving the coagulating bath were drawn in air in aratio of 1.1, washed with water and then drawn in boiling water in aratio of 4.05, with a final filament speed of 60 m/minute. After washingwith water, sizing and drying, the resulting filaments had the followingproperties:

    ______________________________________                                        Gauge per strand       3.3 dtex                                               Tensile strength       24 g/tex                                               Elongation             15%                                                    Water retention capacity                                                                             52.                                                    ______________________________________                                    

After dissolving the acrylic polymer phase from the resulting filaments,the remaining cellulose phase appeared in the form of a continuousthree-dimensional system shown in FIG. 4.

A cross sectional view of the resulting filament (with no acrylicpolymer phase being dissolved therefrom) is shown in FIG. 5, whichclearly reveals the two systems, the clearer system being that of thecellulose phase.

In Examples 16-19, in the preparation of samples of the cellulose phase,by dissolving the acrylonitrile polymer phase from the filaments, toproduce the system illustrated in FIGS. 1-4, the acrylonitrile polymerphase was dissolved by dispersing the samples in dimethylformamide.

We claim:
 1. Fibres, filaments and yarns based on cellulose and anacrylonitrile polymer, wherein the weight ratio ofcellulose/acrylonitrile polymer is between 0.1 and 1, each constituentis in the form of a continuous three-dimensional system of which thefibrils, which are orientated approximately along the axis of the fibre,are closely interwoven, and the cellulose is in the form ofmacromolecules which are partially involved in a three-dimensionalcrystal lattice characteristic of cellulose II.
 2. Fibres, filaments andyarns according to claim 1, wherein the fibres, filaments and yarns havea water retention capacity of at least 20, as determined in accordancewith DIN Standard Specification 53-814.
 3. Fibres, filaments and yarnsaccording to claim 2, wherein said water retention capacity is 30-80. 4.Process for the production of yarns and fibres comprising extruding asolution consisting essentially of (a) cellulose having a degree ofpolymerisation of at least 200, (b) an acrylonitrile polymer, (c)dimethylsulphoxide and (d) formaldehyde.the weight ratio ofcellulose/acrylic polymer being between 0.1 and 1, the weight ratio offormaldehyde/cellulose being between 0.2 and 2 and the total polymerconcentration being between 18 and 30% by weight into a coagulating bathconsisting essentially of 25 to 80% by volume of water and 75 to 20% byvolume of dimethylsulphoxide, said bath being maintained at atemperature between 0° and 40° C., the filaments are thereafterorientated, and the filaments are at least substantially freed ofsolvent.
 5. Process according to claim 4, wherein said solution has atotal polymer concentration of between 18 and 26% by weight.
 6. Processaccording to claim 4, wherein the filaments are orientated by drawing.7. Process according to claim 4, wherein the filaments are washed withwater.
 8. Process according to claim 4, wherein the filaments are washedwith dilute aqueous ammonia solution.